Air moves out of the lungs when:

When blood pH falls (i.e., the blood becomes pore acidic), a negative feedback loop is triggered that increases the rate and depth of ventilation to remove carbon dioxide from the blood.

This is a major mediator of inflammatory responses and causes vasodilation:

The pressure between the visceral and the parietal pleura is always negative, below the atmospheric pressure.

Where on the figure is the epiglottis?  Enter the corresponding letter for this structure.

Where on the figure the cricoid cartilage?  Enter the corresponding letter for this structure.

T-helper cells express the following surface molecules: 

This group of proteins is activated by a series of reactions, in which one activated chemical then activates another; and promotes inflammation, phagocytosis, and cell lysis:

The air in the conducting zone that does not reach the respiratory zone is called:

T- cells require antigen presentation.